The invention relates to a method for feeding molten metal, in particular molten aluminum or a molten aluminum alloy, by means of a nozzle which is horizontally displaceable and vertically adjustable on a carriage, into the adjustable roll gap of two casting rolls of a horizontal strip caster, the feeding of the nozzle being interrupted for the exchange or cleaning thereof, and the carriage being removed from and returned to the region of the casting rolls. The invention also relates to a strip caster for carrying out the method.
Known horizontal strip casters possess, in accordance with a first alternative embodiment, two casting rolls arranged one above the other (e.g. LAUENER Roll Caster), and in accordance with a second alternative embodiment two casting belts (e.g. HAZELETT) or caterpillar molds (e.g. LAUENER Block Caster) rotating one above the other, which are retained by a machine frame or are arranged in a housing. In the preceding section and in what follows, the machine components forming the roll gap are, in accordance with the preferred form of embodiment, referred to only as casting rolls. Above and in what follows, this term also analogously encompasses strip casters with rotating casting belts and caterpillar molds.
In the region of the roll gap or casting gap, a nozzle is situated in the working position between the two casting rolls and is generally fixed to the machine frame. A casting trough, also referred to as a molten metal distribution trough, fed by a casting launder system conducts liquid metal into the nozzle. Although this nozzle can be installed and removed together with its nozzle holder, accessibility is greatly impeded, particularly by a machine frame.
U.S. Pat. No. 4,577,672 (corresponding to French Patent 2,534,500) describes a nozzle unit which is independent of the remainder of the horizontal strip caster and permits precise positioning of the nozzle with reference to the casting gap. This nozzle unit is arranged on a nozzle beam, which is mounted on a carriage that can be moved in the casting direction by a drive. The nozzle can also be displaced in the vertical direction. The horizontal and vertical movements have a fine adjustment which permits exact positioning of the nozzle. This is particularly advantageous during a nozzle change or cleaning of the nozzle, since the nozzle can be removed from the region of the casting rolls for this purpose and repositioned precisely after the necessary work.
Although the solution according to U.S. Pat. No. 4,577,672 provides substantial advantages, it also contains some disadvantages. Before the nozzle is exchanged or cleaned, the casting launder has to be lifted or swivelled away laterally, and it is necessary for the molten metal it contains to be emptied as far as the holding furnace. During the exchange or cleaning of the nozzle, the lifted or swivelled away empty launder cools. Before the strip caster becomes operational again, it is necessary not only to position the nozzle and swing back the launder, but also to preheat the launder. The result is an interruption of work for a total of about 1-2 hours, which is of considerable importance, particularly when the exchange or cleaning operation is repeated one or more times.